1. Field of the Invention
The present invention relates to missile systems, and more particularly to multi-stage missile systems having geometrical constraints.
2. Description of Prior Art
Rocket motors tend to be most efficient when they are long and skinny, with ratios of 4:1 to 5:1 length to diameter being in the realm of the most efficient. With ratios greater than 5:1 vibration problems and propellant grain problems occur which reduce the efficiency. For lower ratios the weight of the motor case, particularly the dome plate on the end opposite the nozzle, causes a reduced efficiency.
For conventional fixed site missiles with no geometric constraints each subsequent stage is approximately one-third the weight of the preceding stage and results in a stepped configuration (FIG. 1), each stage with near optimum length to diameter ratios. For missiles which are required to be readily transportable or which are launched from tubes having geometrical limitations, the geometrical limitations result in a missile wherein the ratios for the motors are not optimum. For example, FIG. 2 shows a missile which is geometrically constrained to a fixed length, L, and a constant diameter, D. This missile has two boost stages, with the first stage motor having a 3:1 ratio, close to optimum, and the second stage motor having a 1:1 ratio. The payload is located forward of the boost stages in the length, l.
Within the geometrical constraints imposed it is desired to obtain greater range. In addition to the restraints of length and diameter, the maximum weight sustainable by the transport bed and/or the launch platform must be considered, as well as the size of the payload.